The goals of my research are to investigate the cellular and molecular mechanisms of segmental pattern formation in annelids. Much of what we know of segmentation in metazoans comes from studies in insects and more recently vertebrates. For many years the annelid community has adopted a cloning by homology strategy designed to identify key developmental regulatory gene products that were likely to operate in annelid development. This approach has generated significant insights into the cellular and molecular mechanisms that regulate annelid embryogenesis, however little progress has been achieved in identifying regulators of annelid segmental patterning. Although the cloning by homology strategy has been successful and remains meritorious, it possesses an inherent bias. The primary focus of this proposal is to characterize segmentation gene candidates identified from a novel unbiased screen of subtraction libraries from two distinct groups of annelids, the derived leech Helobdella robusta and the basal polychaete Capitella sp I. To my knowledge, this genomic approach represents the first unbiased screen for developmental regulatory gene products between classes of a given animal. From this screen, I will focus on characterizing those developmental regulatory genes expressed at the time of segmentation in annelids as determined by in situ hybridization expression data. I also plan to collect comparative expression data as a means to infer the evolutionary role(s) of lophotrochozoan homologues to the insect segmentation gene hunchback using a cross-species hunchback antibody developed in my lab. My final objective is complete functional studies that target hunchback gene expression using splice-blocking antisense morpholino oligos in two different annelid classes. The aberrant regulation of developmental regulatory genes is responsible for many cancers and degenerative diseases in humans. The characterization of this particular group of genes in diverse animal groups will provide important insights into their evolutionary history and how they mediate their functions at the cellular and molecular level. [unreadable] [unreadable] [unreadable]